Photoassociation of sodium in a Bose-Einstein condensate.

We form ultracold ${\mathrm{Na}}_{2}$ molecules by single-photon photoassociation of a Bose-Einstein condensate, measuring the photoassociation rate, linewidth, and light shift of the $J\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$, $v\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}135$ vibrational level of the ${A}^{1}{\ensuremath{\Sigma}}_{u}^{+}$ molecular state. The photoassociation rate constant increases linearly with intensity, even where it is predicted that many-body effects might limit the rate. Our observations are in good agreement with a two-body theory having no free parameters.